NOTE: This time-line needs to be flushed out, and a Player Safe version generated to post for common knowledge. For now, all information here is assumed OOC until you find it out in game or you're notified by a DM that it's common knowledge or your character knows it for some reason.
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“Pre-History”

Creation

Lachesta tricks the Gods, War of the Gods (Time of Troubles: curse of the Great Desert, Battle between Corellon Larethian and Gruumsh (and other base deity info from base DnD pantheon)

Banishment (aka – Great Intervention, shrine to Wee Jas at the location of the Banishment – Lachesta’s Prime Material fortress)

Establishment of the Sandwalkers

Creation of the Tanar’ri and domination of the Abyss by Lachesta – other evil gods leave seeking to create new home

Creation of the Hells – Tiamat and Hextor, Kurtulmak pushed out (begins enmity)

Spawning of Drow (Corellon Larethian vs. Lolth) – founding of Drow cities and populating of the Underdark, creation of the Eyes of the Matron.

Forest of the Moon grows over the ruins of Lachesta’s fortress, and Wee Jas’ shrine. Guardians placed by Obad-Hai (Werewolves).

Eyrthnul secretly corrupts the Werewolf Guardians as revenge against Obad-Hai’s condemnation of his previous alliance with Lachesta.

The Time of Heroes (The Adventures of Aurakkis, Beljymor, Guurhal (early),

The Rise of the Kingdom of Aurak

Creation of Ortimus
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“History”

Tanar’ri Wars (Destruction of Yondalla, Halflings go mad, The Last Stand, Secret aliance of Lolth and Vecna, The Awakened, Death of Aurakkis & Beljymor, spawning of the Minotaurs, Fall of Aurak, Great Rift, Lachesta escapes into the Abyss, Battle between Lolth and Vecna, Victory of Kurtulmak)

Founding of the Knights of the Last Stand (scouring of the land, purging of evil, etc.)

Creation of the Ogrelands

The Time of Many Nations (Bernhard Lightfinger – one of the original Halflings that went mad – wrote stories about himself as things he imagined he did because he was mad)

Split of the Elven Nation of Endrel (the druid in the marsh, battle vs. Abrax, appearance of the Treekin)

Split of the Dwarven Kingdoms

Unification – the Rise of Sartii – the Guild of Sartii Magi

Rise of Astor

The Rise of the Shadowed Hand – connected to several cults of Nerull, one of which is hidden in Sartarus, another in Elilat, another in Ravannah and in Ispar.
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“Contemporary”

War between the Barbarian Tribes – feuding over who is Beljymor’s descendant (gets territory and rights to the mines, etc.) Evil barb village…

The adventures of Sir Brendor – death of the Falcon and end of the hidden Nerull cult in Sartarus, Sac of the Warlord (Black Scourge) – Creation of Pelorien, Heiron, and Garlan; Creation of the Flying Castle; Rise of the sleeping good dragons, Departure of the Inner Circle

Arrangement between the Drow and the Mino

Rise of the Kobold Empire – War over the Ogrelands, capture of Ordyllis, The PenUltimate Emperor Maugor Whitetooth, Elite Kobold Dragoons!!!

Chronicles of Mishtar – Prodigal son leaves his father (King Gashan) in Sartarus and flees south to establish his own rule in Ravannah, Secession of Ravannah (influences and reasons behind the secession – political climate vis-a-vis Economic Determinism in Greater Sartii), Death of his family, Flees Ravannah, Journey beyond the Great Rift, Training at both of the Warring Dragons (secretly), hiding out in the mountains under the alias Sword Saint.

Split of the Guild of Sartii Magi – founding of the Guild of the Baleful Night.

Unification of the remaining Knights of the Last Stand –
Adventures of Karis Azurewrath – after departure of Brendor, Travels to Ortimus, establishes stronghold, begins war against powers that reside there (Khabarahk, general of Lachesta’s Minions), Riaki (friend of Karis, met in the East)

Rise of Erich – Unification of the Knights of the Last Stand (after departure of Sir Brendor and others), reconstruction of the Three Cities

Rise of Pyromemnus – Rise/Fall of Ravannah, creation of the Order of the Fallen, Rousing of Tiamat and her evil dragons